A subatomic particle and its antiparticle are related by a concept known as particle-antiparticle symmetry. Here are the key differences between a subatomic particle and its antiparticle:
Charge: The most notable difference is in their electric charge. A particle and its antiparticle have opposite electric charges. For example, an electron has a negative charge (-1), while its antiparticle, the positron, has a positive charge (+1). Similarly, a proton has a positive charge (+1), while its antiparticle, the antiproton, has a negative charge (-1).
Quantum Numbers: Subatomic particles and their antiparticles differ in their quantum numbers, which are properties that characterize particles in quantum mechanics. These quantum numbers include spin, lepton number, baryon number, isospin, and others. The values of these quantum numbers for a particle and its antiparticle are opposite.
Mass: In some cases, the mass of a particle and its antiparticle may be the same, such as in the case of photons and their antiparticles, which are also photons. However, in other cases, the masses may differ. For example, an electron has a much smaller mass compared to a positron.
Stability: Particle-antiparticle pairs may differ in their stability. Some particles, like electrons, are stable and have a long lifetime, while others, like some of the mesons, are unstable and have very short lifetimes. Antiparticles also tend to be short-lived if they encounter their corresponding particles in the surrounding environment.
When a particle and its antiparticle encounter each other, they can annihilate each other, resulting in the production of energy. This process conserves properties like charge, momentum, and energy. However, it's important to note that not all particles have antiparticles. For example, the photon is its own antiparticle, and certain particles called Majorana fermions are theorized to be their own antiparticles.
In summary, the main differences between a subatomic particle and its antiparticle lie in their electric charge, quantum numbers, mass (which can be the same or different), and stability characteristics.